Various types of solid-state image sensing devices such as CCD image sensors, CMOS-type image sensors, or the like used generally for electron cameras have narrower dynamic ranges than those of subjects to be shot, which is problematic. This has sometimes caused highlight clipping in high brightness regions and shadow clipping in low brightness regions. In view of this problem, a method is proposed in which a plurality of image signals with different exposures are obtained by bracketing, and an image signal for one image having a wide dynamic range is generated by synthesizing those image signals. For example, an image signal having a wide dynamic range is generated by obtaining and synthesizing three image signals with different exposures: an image signal obtained at the center exposure; an image signal obtained at the exposure one step higher than the center exposure; and an image signal obtained at the exposure one step lower than the center exposure.
However, there has been a problem in which the resultant synthesized image signal involves artifacts such as double images or the like because of camera shaking occurring when a plurality of image signals are picked up.
In view of this, as a method of performing bracketing so as to avoid camera shaking, there is a method in which a plurality of image signals are obtained using underexposure, which permits higher shutter speed, and three image signals with different exposures are obtained by synthesizing different numbers of image signals (See Patent Document 1). By further synthesizing the three image signals obtained by bracketing, an image signal having a wide dynamic range is generated. In such a case, three image signals with different exposures can be obtained while avoiding camera shaking, making it possible to prevent artifacts such as double images or the like from occurring in the resultant synthesized image signal.    Patent Document 1: Japanese Laid-open Patent Publication No. 2008-118389